Peripheral ameloblastoma: Review of the literature and report of recurrence as severe dysplasia

Abstract

The peripheral ameloblastoma is a rare odontogenic soft tissue tumor,1,2 which has been reported to account for approximately 1% to 5% of all ameloblastomas.2,3 It was first described in the literature by Kuru in 1911.4 The tumor is distinguished from its intraosseous counterpart by its extraosseous location and its less aggressive behavior, causing mild saucerization of adjacent bone in some instances, but without actual infiltration into the marrow spaces.1,2,5-7 The peripheral ameloblastoma is thought to arise from rests of the dental lamina or from basal cells of the surface epithelium.1,3,6-8 Histologically, the peripheral ameloblastoma resembles the intraosseous form, consisting of a proliferation of ameloblastic epithelium set in a dense collagenous stroma.1,2,5-7,9 Although the lesion has been reported to appear in acanthomatous, follicular, plexiform, and mixed patterns, there is disparity among authors as to which presentation is predominant, with some studies citing the acanthomatous type5,7,10-12 and a few pointing to the plexiform and follicular types.2,3 The recommended treatment is wide excision down through periosteum.1,7,10 Recurrence has been noted infrequently.2,3,7,8 This report describes a case in which a peripheral ameloblastoma was excised, and a new lesion was observed in the same site approximately one year postoperatively. On biopsy, the specimen exhibited severe dysplastic changes microscopically. Six months later, an additional lesion was noted in the same region, which again proved to be dysplastic histologically. Although a handful of recurrent peripheral ameloblastomas have been documented,10,13-15 even fewer lesions have been noted to undergo malignant transformation.3,7,15 This case is believed to be the first arising in the site of a previously excised peripheral ameloblastoma in which solely dysplasia was seen.